Annealing behavior during heating rate of ultrafine-grained 5052 Al alloy deformed at cryogenic temperature

摘要

The microstructural evolution during thermal annealing of a cryogenic rolled 5052 Al alloy was investigated. The activation energy for annealing behavior was calculated using DSC data. For the heating rate of 16℃/min, the precipitation occurred at the annealing temperature of 150-230 ℃ due to Mg self diffusion, recovery occurred at the annealing temperature of 230～260℃, and recrystallization proceeded at a higher temperature up to about 370℃. Both recovery and recrystallization gave rise to non-uniform, bimodal grain-size distributions, which may result from heterogeneous nanostructures. In addition, the activation energy for the precipitation was found as ～115kJ/mol, indicating the process was diffusion-controlled (Mg in Al), and the activation energy for recovery was found to be ～140kJ/mol, representing self-diffusion in pure Al.